The proposed research will determine the role of arachidonic acid and other prostaglandin precursors on the cardiovascular system of the dog. The corresponding endoperoxides will be synthesized and compared with the precursor acids and prostaglandins in the presence and absence of cyclo oxygenase inhibitors to determine whether the effects of the precursors are mediated through the observed vascular properties of the endoperoxides or the prostaglandins. The in vivo studies will be corroborated and extended with vascular strips; the role of arachidonic acid as a mediator of endogenous vasoactive substances will be studied by estimation of this acid, endoperoxide and prostaglandins. BIBLIOGRAPHIC REFERENCES: "Arachidonic Acid and iPGE and iPGF levels in Human Urine", L. Beckmann, E. Leovey, C. Armstrong, P. W. Ramwell, Abstract, Am. Fed. for Clin. Res., 1977. "Action of PGI and Related Compounds on Human Platelet Aggregation", B. E. Crane, T.L. Maish, Y. T. Maddox, E. J. Corey, and P. W. Ramwell, Abstract, Am. Fed. for Clin. Res., 1977.